Automotive heat exchanger assemblies commonly have a core comprising tubes, separators or fins, and side plates made of some type of metal, such as aluminum, and associated headers. These heat exchangers also comprise end tanks or manifolds made of plastic or metal. The purpose of the header is to attach the end tank or manifold firmly to the core portion of the heat exchanger. To provide for efficient heat exchange and to avoid potentially overheating due to loss of thermal liquid or gas within the heat exchanger, the tank to header joints must be essentially leak-proof. Typically the tank to header joints are made ‘leak tight’ by providing for a seal, such as a rubber gasket, between the header and the tank.
The problem with current designs is that the gasket, and, in particular, the rubber gasket often used between the header and the tank, is often misaligned or otherwise improperly positioned, either due to improper assembly procedures or faulty design of seal or gasket. Such a misalignment or ‘defect’ is often not detectable at the first stages of assembly or testing, due to the fact that the location of the seal is not visible on external examination. Detection of the defect is made more difficult since the seal, though defective, may make the tank to header joint appear to be leak proof and the heat exchanger may appear to be functioning properly, due to the fact that the misalignment or otherwise improper positioning of the gasket lead to it somehow being ‘wedged’ or ‘pinched’ in place during assembly, leading to the formation of a temporary seal. Since this temporary seal may be capable of lasting through traditional leak testing procedures performed after initial assembly at the manufacturing facility, the fact that it is defective vis-à-vis its use in the normal heat exchanger operating environment, may not be apparent until the heat exchanger is shipped to a customer assembly plant for further processing, or even during vehicle use by the end customer, which can lead to disastrous consequences.
One approach to solving this problem is illustrated in U.S. Pat. No. 5,899,267, which adds ribs which project from the interior wall of the end tank in order to hold in a gasket that is incorrectly positioned so that it can form a seal, while nevertheless, allowing the defective or not properly assembled joint gasket to exist and to hold back or contain fluid. The ribs may also prevent an inappropriately positioned gasket from being displaced during initial leak testing, to prevent the catastrophic loss of fluid. In addition, inappropriately positioned and/or pinched gaskets can have resultant tears and/or induced gasket surface defects or flaws, that reduce the life of the seal, and, thus, the effective lifetime of the heat exchanger assembly. The solution of U.S. Pat. No. 5,899,267 may, therefore, lead to the unexpected effect of shipping parts, with improperly positioned gaskets and/or other defects or flaws, to the customer or end consumer.
The heat exchanger assemblies of the present invention, with means to detect temporary seals at the tank to header joint, as described below, have not been described in this prior art.